Device for portrayal of complex waves



' Dec. 20, 1949 R. K. POTTER 2,492,062

DEVICE FOR PORTRAYAL OF COMPLEX WAVES Filed Nov. 5, 194:6 2 Sheets-Sheet l 1 22 H ROTOR PAPER TAPE gag/r51? wvawroxe R. K. POT TER EPZPQ Q ATT RNEV Dec. 20, 1949 R. K. POTTER 2,492,062

DEVICE FOR PORTRAYAL 0F COMPLEX WAVES I Filed Nov. 5, 1946 2 Shee tS-Sheet 2 PRINTER FREQUENCY awe SHALL WIN /N 5 N TOR RKPOTTER BY Giza M ATTO NEV Patented Dec. 20, 1949 UNITED STATES PATENT OFFICE DEVICE FOR PORTRAYAL OF COMPLEX WAVES Ralph K. Potter, Morristown, N. J., assignor to Bell Telephone Laboratories,

Incorporated,

This invention relates to the analysis and visual representation of complex waves and more particularly to the visual representation of speech waves and the like.

An object of the invention is to record intelligible voice ener y patterns on a tape, sheet or other permanent impression-taking medium.

Another object of the invention is the provision of a visual telephony system in which, as a sequence of syllables or words are produced by a speaker, a permanent printed record of patterns or symbols respective to the syllables or words is made.

Still another object is to translate or convert a speech sound or a sequence of speech sounds into a printed record of a visual pattern or patterns respective to the speech sound or sequence of speech sounds.

In the present inventors United States Patent 2,403,997, issued July 16, 1946, means and method are disclosed for the visual representation of complex waves and, more specifically, of those corresponding to speech sounds, in the form of word pictures or patterns. As explained in detail in that patent, an intelligible visually comprehensible pattern respective to a distinctly spoken word or syllable may be pictorially presented on a fluorescent viewing area, for example, the screen of a cathode ray oscilloscope, on an electrosensitive chart, or on a photosensitive surface. In accordance with the present invention, means are provided whereby such word or syllable patterns may be presented as a printed record on a tape, sheet or other permanent-impression accepting medium.

A more complete understanding of the invention will be obtained from the detailed description that follows, taken in conjunction with the appended drawings, wherein:

Fig. 1 illustrates one arrangement of a word or syllable pattern printing system in accordance with the invention;

Fig. 2 illustrates another embodiment of the invention; and

Fig. 3 is a reproduction of a typical visual representation obtained with the Fig. 1 system.

The arrangement shown in Fig. 1 comprises a sound wave energy pick-up device or microphone In, an audio frequency current amplifier ii and a plurality of frequency selective channels I2 for deriving a corresponding plurality of control signals from the complex electric waves corresponding to the distinct speech sounds that are directed against the microphone. Each of the frequency selective channels comprises a bandpass filter l3, a circuit I4 for rectifying the output of the band-pass filter, a narrow band lowpass filter I5, and a potentiometer l6. The bandpass filters may have pass bands of approximately the same width, each embracing a different band but together covering the frequency range of the expected output of the amplifier H. For example, if it is assumed that the frequency range of interest is that of zero to approximately 3,000 cycles per second, each band-pass filter could be assigned a band width of approximately 300 cycles. The rectifying circuit may be a fullwave rectifier, for example, of the copper-oxide type. The low-pass filters may be similar to one another and have an upper cut-01f frequency of low value, for example, of the order of 25 cycles per second. The adjustable contact of each potentiometer is connected to a respective section or segment I! of a commutator Hi. The commutator [8 comprises an outer ring of the arcuate, spaced sections ll, an inner ring member l9 concentric with the outer ring, and a rotatable contact arm 20 insulatingly supporting a contact brush 2| adapted to interconnect the inner and outer rings of the commutator. The arm 20 is mounted on a shaft 22 of a motor 23, and is adapted for rotation with the shaft as the latter is driven by the motor at a uniform rate of many revolutions per second. The commutator thereby enables a repeated sequential scanning of the outputs of the respective frequency selective channels. A direct current amplifier 24 is connected with the commutator, and includes in its output circuit a fast operating, rapid-releasing relay or switch 25, which may be of the type described in Ellwood Patent 2,289,830 of July 14, 194.2. This switch contains a pair of normallyopen contact springs 26, -27 of magnetic material, sealed Within a gas-filled enclosure, and adapted to close under control of associated magnetizing coil 28 upon flow of current of appropriate strength through the latter. The direct current amplifier in the specific arrangement being described is provided to increase the sensitivity of the relay.

Also mounted on the shaft 22 and adapted for rotation therewith, is the rotor 29 of a printer mechanism 30. The rotor 29 may comprise a substantially cylindrical body having a helical ridge or projection St on its outer surface extending circumferentially of the cylindrical body and between the ends of the latter. An ink pad roller 32 is adapted for rotation against the printer rotor to continuously apply appropriate ink to the helical ridge. The printer mechanism also 3 includes electromagnet means comprising elec" tromagnet 33 and a pivotally mounted armature 34, which latter supports a printer bar or pressure member 35 at its innermost end and normally positioned in spaced relation to the rotor 29. Energizing current for the electromagnet 33 is supplied from direct current source 36, the direct current path being normally interrupted at the contacts 28, 21, A paper or other recording tape or ribbon 31 is adapted to be fed continuously at a uniform rate between the printer bar and rotor. For purposes of this disclosure, the tape may be considered as moving in a direction normal to and out of the plane of the drawing, and the rotor and ink roller as rotating in the directions indicated by the arrows associated with their respective shafts. When, as will be explained in greater detail hereinafter, the printer bar is caused to press the tape against the printer rotor, an ink mark will be made on the tape by that portion of the length of the helical ridge against which the paper presses. If the rotor is caused to revolve many times a second while the tape is caused to move relative to the rotor at a slow rate, and the printer bar is caused to press the tape against the rotor at intervals during each complete revolution of the rotor, a set of adjacent lines of marks will be produced on the tape, each such line extending across the width of the tape and the successive adjacent lines being built up successively along the longitudinal dimension of the tape or ribbon. By appropriate alignment of the rotor and the commutator, successive adjacent portions of the length of the helical ridge may be made respective to successive adjacent sections of the outer ring of the commutator, and, hence, respective to the component frequency bands into which the received complex wave is separated by the frequency selective channels. Hence, if the successive control currents actuating the printer electromagnet at intervals are provided through the commutator, the marks in each line across the width of the tape will be respective to the successive component frequency bands scanned by the commutator in one complete revolution of the commutator contact arm and the printer rotor, and each adjacent line of such marks will be representative of repeated complete scanning of the frequency range involved at successive later time intervals. Hence, the crosswise dimension or width of the tape may be considered as a frequency coordinate, or axis, and the longitudinal or lengthwise dimension of the tape may be considered as a time coordinate or axis of the pattern that is printed on the tape.

In the analysis of a speech sound and its visual representation as a printed pattern on a recording tape the arrangement of Fig. 1 operates as follows: A speech sound or sequence of speech sounds is caused to actuate the microphone. The resultant complex electric wave corresponding to the speech wave is amplified and, if desired, automatically controlled in volume, and transmitted to the frequency selective channels. The latter separate the frequencies into a plurality of preassigned adjacent component frequency bands, and convert the speech energy in each band into a control signal respective to said band, and varying in amplitude with respect to time and with respect to the specific frequencies present in the particular component frequency band with respect to time. Simultaneously, the commutator and the printer rotor are revolving at a rate of many times per second. The successive pulses or signals derived from the potentiometers of the frequency selective channels through the commutator, are applied to the input stage of the direct current amplifier. If a specific amplified pulse is of preassigned minimum amplitude, the increased current flow in winding 28 causes contacts 26, 21 to engage closing an energizing circuit for the electromagnet 33 from the source 35. The attraction of the outer end of the armature, on the front side of the pivot, causes the printer bar end of the armature, on the rear side of the pivot, to press against the paper tape to cause the latter to make contact with the spiral or helical ridge on the printer rotor. If, for one complete cycle of the commutator, the successive pulses corresponding to the successive component frequency bands scanned .by the commutator exceed the preassigned minimum signal strength required, the tape and the helical ridge will be brought into engagement a number of times equal to the number of commutator segments, that is, once for each of the component frequency bands. Hence, for one scanning of the frequency range, a sequence or series of adjacent marks appears substantially on a line across the width of the paper tape. If some number of successive pulses less than the number of component frequency bands causes operation of the printer bar, marks will appear on the tape only for such lesser number of component bands, and respective only to the particular bands from which such pulses are derived. As the paper tape is moved or fed slowly between the printer bar and rotor and the frequency range is scanned many times a second, a set of adjacent records of such sequences of marks is obtained to build up a visual pattern respective to the particular speech sound or a series of visual patterns respective to the particular succession of speech sounds. Each succeeding line of marks presents for the particular time interval represented by the scanning interval, the energy distribution by frequency of the speech sound for that time interval, and generally'will vary slightly atleast and frequently substantially from a preceding or a succeeding line of marks. Fig. 3 is illustrative of the pattern obtainable with an arrangement similar to Fig. 1 for the speech sounds represented by the words we shall win and is reproduced from a tape on which these and other words were recorded. The rotor printer actually used included a second helical ridge which constituted a continuation of a first helical ridge or spiral, hence the visual pattern for each syllable appears twice, one above the other in the figure. In the particular instance, the paper was moved forwardly at a rate of slightly less than one inch per second, and the frequency range of the speech sounds was scanned at the rate of approximately sixty times per second. A high scanning rate for a given rate of tape movement appears to contribute a higher order of resolution to the pattern. It has been found that, for different voices, substantially the same printed patterns are obtainable for the same speech sounds, and are intelligible and readily comprehensible to a trained observer.

Fig. 2 shows another arrangement embodying the present invention. In Fig. 2 the speech sound or sequence of speech sounds is converted by the microphone Ill into a complex electric wave corresponding to such sound or sounds, amplified and volume-controlled in amplifier H, and impressed on the input of a balanced modue lator 40. Beating or carrier waves from a variable frequency oscillator 4| .are applied to the modulator at the same time. The modulator may be of the carrier suppression type, and the sidebands that are produced are applied to a filter er of the narrow pass-band type. The band of waves passed by the filter 42 are rectified in the rectifying circuit 43, amplified by amplifier means 4 3, and applied to the energizing winding of an electromagnet d5 of a printer mechanism including an armature 46 and a printer rotor 29, printer bar 35 and recording tape 31 similar to those of the arrangement of Fig. 1. The motor 41 for driving the oscillator also drives the printer rotor, causing it to make one revolution for each sweep of the oscillator between its extreme frequencies. The frequency of the oscillator is continuously and repeatedly varied over a predetermined range in such relation to the frequency position of the band passed by the filter 42, that as the frequency of the oscillator is varied from one extreme to another, one of the sidebands produced by the modulator is swept completely across the pass band of the filter. The electric wave corresponding to the speech sound or sequence of sounds is scanned many times a second by the frequency analyzer and during each scanning process the signal or pulse applied to the electromagnet Q5 varies respective to the wave power found in each successive band.

As the printer rotor 29 revolves in synchronism with the oscillator, an incremental portion only of the helical or spiral ridge 3! will be immediately opposite the recording tape 31 and the printer bar 35 at any one instant. Each incremental portion of the helical ridge will be respective to a component frequency band of the range of frequencies in the wave being analyzed. Whenever the rectified output of the scanning filter is sufficient to actuate the armature, the latter will cause the printer bar to press the helical ridge and the paper tape into contact to result in a mark on the paper. For one complete scanning of the frequency range of the speech sounds being studied, a sequence of such marks respective to the successive frequency components scanned by the scanning filter will be made across the width of the tape or sheet. For each repeated complete scanning, another sequence of marks will be produced adjacent the preceding set. In this way, a printed pattern corresponding to the speech sounds may be built up in which the crosswise dimension of the tape constitutes a frequency axis and a longitudinal or lengthwise dimension of the tape constitutes a time axis. The variation in the wave power of a speech sound or sequence of speech sounds with frequency and time may be emphasized in the resultant pattern by appropriate selection of the material of the printer bar, for example, the latter might comprise a resilient member, or be constructed of a resilient material, such as rubber.

Although the invention has been disclosed with reference to certain specific embodiments, it will be understood that modifications therein will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In combination, means for receiving electric waves lying within a predetermined frequency range, frequency selective wave translating means connected thereto having a narrow bandpass characteristic, means for effectively sweeping the pass band of said selective means periodically across the said frequency range, and means for printing a visual pattern respective to said electric waves, said means comprising a .movmg record ribbon, printing mechanism movable relative to and repetitively across the direction of movement of said ribbon in synchronism with the repeated'scanning of said frequency range, and means actuated under the control of the wave energy passed by said wave translating means for causing contact engagement between said ribbon and said printing mechanism for the marking of said ribbon.

2. In combination, a source of complex electric Waves corresponding to speech sounds, frequency analyzer means for traversing the wave frequency range many times per second and each time selecting a different frequency component of the waves in predetermined succession, and means for making a visual record respective to the said waves, said last-mentioned means comprising a moving record sheet, a printing member movable relative to and repeatedly across the direction of movement of said sheet in synchronism with the repeated traverse of said frequency range, and means comprising a pressure member for producing contact engagement between said record sheet and said printing member, said pressure member being actuated under control of said selected frequency components.

3. In combination, means for converting speech bearing acoustic energy into electric wave energy correspondin thereto, means for separating said electric wave energy into a plurality of component frequency bands, means for scanning said component bands successively and repeatedly many times per second, and means for printing a visual pattern corresponding to said speech energy, said means comprising a moving record sheet, printing mechanism movable relative to and repeatedly across the direction of said sheet in synchronism with the repeated scanning of said frequency bands, and means actuated under the control of the said frequency component bands for causing contact between said record sheet and said printing mechanism.

4. The combination as claimed in claim 3 in which said printing mechanism includes a member having a helical ridge portion extending circumferentially and longitudinally thereof, incremental lengths of said ridge being respective to said frequency component bands.

5. In combination, a receiver of speech bearing waves, a plurality of frequency selective means for concurrently dividing the frequency range of said waves into a plurality of component frequency bands, means for deriving from said waves a plurality of control signals respective to the component frequency bands, means for making a visual printed record respective to said waves, said means comprising a moving record sheet, a printing mechanism movable relative to and across the direction of movement of said sheet, a pressure member for causing contact engagement between said sheet and said mechanism and means for actuating said pressure member, and means for applying said control signals in sequence and repeatedly many times a second to said actuating means while simultaneously causin said printing mechanism to move relative to and across the direction of movement of said sheet in synchronism with the repeated application of the sequence of control signals to the actuating means.

RALPH K. POTTER.

(References on following page) The following references are of record in the 7 REFERENCES CITED file of this patent:

Number UNITED STATES PATENTS Number 2,181,265 2,213,876

Name Da'te Dudley Nov. 28, 1939 Young Sept. 3, 1940 Lacy July 16, 1946 Potter July 16, 1946 Buhrendorf Aug. 2'7, 1946 Feldman June 24, 1947 

